Firing pin safety mechanism for an externally powered automatic gun



Feb. 14, 1967 c. E. LANIZZANI 3,303,743

FIRING PIN SAFETY MECHANISM FOR AN EXTERNALLY POWERED AUTOMATIC GUN 5 Sheets-Sheet 1 Filed March 13, 1965 1 m 1 m m u T 1 w w w W h m 40 m E m 3 m Q 1 mm iii mm fi m mm 4% l v mm O @Q Q N9 N9 y NI Em v9 1 Feb. 14, 1967 c. E. LANIZZANI 3,303,743

FIRING PIN SAFETY MECHANISM FOR AN EXTERNALLY POWERED AUTOMATIC GUN Filed March 13, 1963 3 Sheets-Sheet 2 Eig L1.

* i INVENTOR.

* ifi EhILT1E5E LU11iZZ11Di 3,3tl3fi4 3 FIRIING lliN SAFETY MECHANIISM Filth AN EX- TERNALLY PG WERED AUTOMATIC GUN Charles E. Lanizzani, Stafiord, Conn., assignor to the United States of America as represented by the Secretary of the Army Filed Mar. f3, 1963, Ser. No. 265,593 6 Claims. (U. 39-l4) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

. This invention relates to automatic guns wherein the operating parts are controlled by an externally powered drum and is more specifically directed to a hammer-actuated firing mechanism therefor.

Current military tactics require a universal machine gun which can be employed against such diverse targets as aircraft, ground vehicles, and personnel with equal effectiveness. This has been satisfactorily achieved in a recent gun design wherein the chambering of each cartridge is accomplished by the rearward movement of a longitudinally reciprocal barrel which is actuated by a helical cam track provided in a rotatable drum. Additional cam tracks in the drum serve to feed the cartridges into the gun and to lock the barrel in battery position. The drum is, in turn, driven by an electric motor with a variable output which can be readily adjusted to provide the rotational velocity necessary to operate the gun at the rate of fire most suitable for use against the particular target against which the gun is being aimed.

Firing of each cartridge is accomplished by utilizing the locking movement of the barrel lock to actuate a scar out of cocking engagement with a pivotal hammer which is thereby released for impact with a longitudinally slidable firing pin normally held to the rear by a suitable spring. While this firing mechanism is currently acceptable,'considerable concern is being expressed over the possibility of premature discharge of the cartridge in the event of any accidental release of the hammer during the cocking movement imparted thereto by the rearward travel of the barrel. Furthermore, due to the relatively short travel of the barrel lock, some difficulty has been experienced in coordinating the corresponding movement of the hammer to ensure the release thereof from the sear prior to the completion of the unlocking movement of the barrel lock.

Accordingly, it is a general object of this invention to provide a hammer-operated firing mechanism of improved safety for an automatic gun operated by a rotatable drum driven by an external source of power.

It is a further and more specific object of the present invention to provide a firing mechanism for the aforesaid gun wherein the hammer is released independently of the locking of the barrel so that both functions can be accomplished in optimum timing relationship.

Another object of this invention is to provide a firing mechanism for the aforesaid gun in which the firing pin is securely blocked against premature firing movement until the hammer is released from the cocked position thereof.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a longitudinal section of an externally powered gun with the firing mechanism of this invention at the instant of discharge of the chambered cartridge;

FIG. 2 is an enlarged sectional view taken along line 2-2 in FIG. 1 to show the firing mechanism as seen from the rear;

FIG. 3 is an enlarged sectional view taken along line 3-3 in FIG. 2 but with the parts in the position assumed 3,3fi3,743 Patented Feb. 14, 1967 at the completion of the forward travel of the barrel to show the manner in which accidental forward movement of the firing pin is blocked;

FIG. 4 is an enlarged fragmentary sectional view taken along line 4-4 in FIG. 1 to show the configuration of the firing and barrel locking cam tracks; and

FIG. 5 is an enlarged view similar to FIG. 1 but limited to the rear end of the gun to show the positions of the various parts of the firing mechanism immediately prior to completion of the cocking movement of the hammer.

The present invention essentially comprises a firing pin blocking member which is pivotally secured to the free end of a link depending from an elongated firing lever pivotally mounted in the receiver and utilized to disengage the sear from the hammer in response to a firing cam on a rotating drum. The blocking member is also pivotally secured in the receiver so that whenever the firing lever is not in contact with the firing cam on the drum, the link is returned to the lowermost position thereof in which the blocking member is pivoted to prevent forward movement of the firing pin until the firing lever is again actuated to release the sear from the hammer after the barrel has been locked in battery position.

The foregoing invention is particularly adapted for an externally powered automatic gun of the type disclosed in my copending patent application, Serial No. 246,862 filed December 14, 1962. As shown in the drawings, this gun includes a receiver 12 provided with a forwardly opening central bore 14 adapted to slidably receive a reciprocal barrel 16. Receiver 12 is forwardly extended in coaxial alignment with bore 14 to form a tubular housing 18 about barrel 16. A hollow cylindrical drum 20 is con centrically mounted on housing 18 for rotation therearound by means of internally disposed front and rear roller bearings 22 and 24, respectively.

The rear end of drum 26 is provided with an annular ring gear 26 adapted to mesh with a gear assembly 28 on a variable output motor 30 mounted on a bracket 32 attached to the top of receiver 12. The hollow interior of drum 20 is provided with a helical cam track 34 engageable with a follower 36 projecting upwardly from barrel 16 through housing 18. Thus, rotation of drum 20 serves to reciprocate barrel 16 into and out of battery position. The rear face of ring gear 26 is provided with an eccentric cam track 38 engageable with a follower 49 adapted to actuate suitable feed mechanism (not shown) for intermittently feeding the leading cartridge 42 of a linked belt into position to be chambered by the rearward movement of barrel 16 into battery position.

Ring gear 26 also includes a cam track 44 in the front face thereof engageable with a follower roller 46 projecting rearwardly from a barrel lock 38 slidably mounted in barrel housing 18 for vertical movement into and out of locking engagement with an annular groove 59 in barrel 16. The camming portions in cam tracks 34 and 38 are specifically located to insure that the feeding movement of the cartridge belt is limited to the period in which the breech end of barrel 16 is spaced forwardly of the rear wall of receiver bore 14 at a distance exceeding the length of cartridge 42. In addition, the location of the camming portion of cam track 44- is such that the movements of barrel lock 48 are limited to the period in which barrel 16 is disposed in battery position.

The discharge of each cartridge 42 is accomplished by a firing pin 52 slidably disposed in the center of a plug 53 which is, in turn, threadably secured in the rear end of a counterbored hole 54 extending through the rear wall of receiver 12 to communicate with bore 14 therein. The extreme forward shoulder 58 formed by the counterbore in firing pin hole 54 provides a seat for a coil spring 60 whose rear end bears against an annular flange 62 on 9 firing pin 52. Spring 60 normally positions firing pin 52 so that the tip thereof is withdrawn into hole 54 while the rear end thereof protrudes from receiver 12, as best shown in FIG. 5, for impact by the front face of a hammer 641.

A housing 66 is suitably attached to the rear end of receiver 12 by bolts 67 and is provided with a hollow interior in which hammer 64 is rotatably mounted on a transverse pin 68 fixedly secured in the opposing sidewalls of housing 66 adjacent the bottom thereof. A helically wound spring 70 is formed in two separate sections to surround pin 68 on both sides of hammer 64. These sections are joined by a substantially rectangular coil 72 which bears against the rear of hammer 64 to normally impart clockwise rotation thereto.

The right side of hammer 64, as viewed from the rear, is cut away to form a forwardly facing shoulder 74 disposed immediately to the rear of a pawl 76 rotatably mounted on an outwardly projecting cylindrical stud 78. Pawl 76 is normally biased into engagement with shoulder 74 by a suitable coil spring 77. A cocking rod 811 i slidably seated in a longitudinal hole 82 formed into the rear end of receiver 12 and, as shown in FIG. 5, is arranged to be moved to the rear by a lug 84 depending from the underside of barrel 16 adjacent the breech end thereof. The interior of rod as is hollow and contains a coil spring 86 which is seated against a relatively narrow post 90 extending upwardly from a base 91 fixed in the bottom of housing 66. The rear end of cooking rod 80 is vertically enlarged, as best shown at $2, and is provided with a laterally projecting arm 94 engageable with a finger 98 projecting upwardly from pawl 76 for a purpose to be hereinafter shown.

The upper end of hammer 64 is formed with a cocking notch 100 arranged to engage with a correspondingly formed projection 1112 depending from the underside of a sear 1M pivotally mounted in housing 66 by a transverse pin 166. A torsion spring 111% surrounds pin 1116 and terminates in an extension 1111 which bears against the top of sear 164 to urge the latter into cocking engagement with hammer 54. A T-shaped stud 112 projects upwardly from the top of scar 1114 and is engageable with the forked rear end 116 of an elongated firing lever 118 pivotally mounted about a transverse pin 11? in receiver 12 immediately above bore 14 therein.

The rear end of firing lever 118 is S-shaped, as indicated at 1211, for exit from housing 66 through a suitable opening 122 in the upper wall thereof and extends forwardly therefrom in parallel relation with receiver bore 14. The forward end of lever 118 extends into a rearwardly opening groove 124 in a diametrically enlarged portion 125 of barrel housing 18 and terminates directly beneath an arcuate cam 126 formed on the inner periphery of annular ring gear 26 in vertical alignment with the actuating portion of barrel lock cam track 44 as best shown in FIG. 4. A coil spring 127 surrounds pivot pin 119 and normally urges lever 118 in a counterclockwise direction to insure that the forward end thereof will lie in the path of movement of firing cam 126 during each rotation of drum 20. Immediately forwardly of the S-shaped portion 120, firing lever 118 is vertically slotted, as indicated at 128, to fixedly receive the upper end of a depending link 1311 extending into a vertical recess 132 in the rear end of wall of receiver 12. The lower end of link 1311 is bifurcated, as indicated at 134, and is provided with a fixed cross pin 136 on which a firing pin blocking member 138 is pivotally mounted. Blocking member 138 is, at the same time, pivotally pinned, as shown at 140, between the sidewalls of receiver recess 132. The underside of blocking member 138 is formed with a depending foot 142 which extends into the path of forward movement of a tab 144 projecting upwardly from annular flange 62 on firing pin 52. When the center of cross pin 35 lies in longitudinal alignment with pivot point 140 of blocking member 1?8, as best shown in FIG.

3- 3, foot 142 is held stationary in blocking engagement with tab 1 4 on firing pin 52.

As a result of the foregoing structure, each cycle of rotation of drum 20 brings cam on ring gear 26 into engagement with the forward end of firing lever 118 to impart clockwise pivotal movement thereto whereupon the rear end thereof, which is in engagement with T-shaped stud 112, is raised to lift sear 104 out of cocking engagement with hammer 64. This upward movement of the rear end of firing lever 118 also raises link to elevate the forward end of firing pin blocking member 138 above pivot pin as best hown in FIG. 1. As a result, member 138 is free to be pivoted about pin 1411 in response to the forward movement imparted to firing pin 52 by hammer 64. In order to permit this pivotal unblocking movement of member 138, the hole through Which cross pin 136 extends is longitudinally elongated as shown at 146. Thus, the fall of hammer 64 will force firing pin 52 into firing contact with the cartridge 42 chambered in barrel 16. As soon a firing cam 126 is rotated out of engagement with the forward end of firing lever 118, the pivotal movement imparted to sear 104 by spring 108 returns firing lever 118 to the prefired position thereof assisted by spring 127. During this return movement of firing lever 118, the downward movement of link 130 pivots blocking member foot 142 against tab 144 to force firing pin 52 to the rear whereupon this position is maintained while pivot pins 136 and 140 are in longitudinal axial alignment. The rearward movement imparted to firing pin 52 is of sufficient force to overcome the resistance of hammer spring 711.

The continued rotation of drum 20 functions to unlock barrel 16 for forward movement and to feed the next cartridge 42 in the linked belt into position to be chambered during the subsequent return of barrel 16 to battery position. As barrel 16 is moved to the rear, lug 84 thereon force cocking rod 813 rearwardly so that arm 94 thereof engages finger 98 on cocking pawl 76 to impart corresponding pivotal movement to hammer 64. As shown in FIG. 5, after cocking notch 1% on hammer 64 has overridden projection 1192 on sear 1114, subsequent engagement therebetween is ensured by the respective springs 71) and 1%. The pivotal movement of hammer 64 to the rear is terminated when arm 94 on cocking rod 80 rides over finger 98 on cocking pawl 76 immediately prior to the completion of the rearward movement of barrel 16 into battery position. Barrel 16 is then locked and the cartridge 42 chambered therein is fired as explained above.

Once barrel 16 is unlocked and begins to move forwardly, cocking rod 8% is freed for corresponding forward movement whereupon arm 94 there-on rides over cocking pawl 76 which snaps back into contact with shoulder 74 on the side of hammer 64. As a result, cocking pawl 76 is again positioned to impart cocking movement to hammer 64 during the return of barrel 16 to battery position.

Thus, there is here provided a novel firing mechanism wherein the release of the hammer by the sear is utilized to unblock the firing pin for actuation by the hammer. Consequently, firing of the cartridges is limited to the relatively brief .period in which the barrel is completely locked in bat-tery position and cannot occur in the event of any premature accidental release of the hammer.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variation may be devised within the spirit and scope thereof and the following claims are intended to include such variations.

1; claim:

1. In an automatic gun having a receiver with a forwardly opening bore, a barrel slidably disposed in the bore, and an externally powered rotatable drum having cam means for reciprocating the barrel into and out of locked battery position, the combination of a firing pin slidably-mounted in the receiver, a hammer mounted for pivotal impact with said firing pin, a pivotal sear for retaining said hammer in the cocked position thereof, a firing lever pivotally mounted in the receiver for disengaging said sear from said hammer for release thereof against said firing pin, a link secured to said firing lever to depend therefrom rearwardly of the pivotal engagement of the latter in the receiver, and means pivoted to the depending end of said link for blocking the firing movement of said firing pin during the interval in which the barrel is unlocked, said firing pin blocking means being rendered inoperative in response to the firing movement of said firing lever.

2. The combination defined in claim 1 wherein said means for blocking said firing pin comprises a firing pin blocking member having a front end in pivotal engagement with the lower end of said depending link and a' rear end pivotally secured in the receiver, and a depending foot on said blocking member extending into the path of said firing pin to block the forward firing movement thereof Whenever the front end of said blocking member is pivoted into longitudinal axial alignment with the rear end thereof.

3. In an automatic gun having a receiver with a forwardly opening bore, a barrel slidably disposed in the bore, an externally powered rotatable drum having cam means for reciprocating the barrel into and out of battery position and for locking the barrel to the receiver during the battery position thereof, the combination of a firing pin slidably mounted in the receiver, a hammer mounted for a pivotal impact with said firing pin, a pivotal sear for retaining said hammer in a cocked position, a cocking rod .slidably disposed in the receiver in the rearward path of the breech end of the barrel, a cocking pawl rotatably mounted on the side of said hammer for converting the rearward movement of said cocking rod into pivotal rearward movement of said hammer, a firing lever pivotally mounted in the receiver for rear end engagement with said sear, a firing cam in the drum engageable with the forward end of said firing lever during the interval in which the barrel is in locked battery position whereby the clockwise pivotal movement imparted to said firing lever actuates said sear out of cocking engagement with said hammer, and means connected to said firing lever for blocking the firing movement of said firing pin during the interval in which the barrel is unlocked, said firing pin blocking means being rendered inoperative in response to the firing movement of said firing lever,

4. In an automatic gun having a receiver with a forwardly opening bore, a barrel slidably disposed in the bore, and an externally powered rotatable drum having cam means for reciprocating the barrel into and out of locked battery position, the combination of a firing pin slidabl y mounted in the receiver, a hammer biased for clockwise pivotal movement into impact with said firing pin, a sear biased for counterclockwise pivotal movement into cocking engagement with said hammer, a firing lever pivotally mounted in the receiver with the rear end thereof in engagement with said sear, an elongated link depending vertically from said firing lever and in fixed engagement therewith at a point rearwardly of the pivotal engagement thereof in the receiver, a firing pin blocking member having a forwardly disposed pivot pin for pivotal engagement with the free end of said depending link and having a rearwardly disposed pivot pin in engagement with the receiver, a depending'foot on aid blocking member extending into the path of said firing pin to block the forward firing movement thereof whenever said member is positioned so that said pivot pins thereon are in longitudinal axial alignment, a firing cam located in the drum to engage the forward end of said firing lever during the interval in which the barrel is locked in battery position whereby the clockwise pivotal movement imparted to said firing lever frees said sear from cocking engagement with said hammer and raises said depending link to pivot said foot on said blocking member out of blocking engagement with said firing pin, and spring means in the receiver for returning said firing lever to the unfired position thereof whereupon said sear is repositioned for cocking engagement with said hammer and said blocking member is realigned to block the firing movement of said firing pin.

5. The combination defined in claim 4- wherein the rear end of the receiver is provided with a housing for said sear and said hammer, said housing having openings for the rear ends of said firing lever and said cocking rod.

6. The combination defined in claim 4 wherein the rear end of the receiver is formed with a vertical slot to receive said depending link on said firing lever, and said pivot pin at the rear end of said firing pin blocking member is plivotally mounted between the sidewalls of said vertical 5 0t.

References Cited by the Examiner UNITED STATES PATENTS 574,350 12/1896 Catlin 89-454 BENJAMIN A. BORCHELT, Primary Examiner.

F. C. MATTERN, S. C. BENTLEY, Assistant Examiners. 

1. IN AN AUTOMATIC GUN HAVING A RECEIVER WITH A FORWARDLY OPENING BORE, A BARREL SLIDABLY DISPOSED IN THE BORE, AND AN EXTERNALLY POWERED ROTATABLE DRUM HAVING CAM MEANS FOR RECIPROCATING THE BARREL INTO AND OUT OF LOCKED BATTERY POSITION, THE COMBINATION OF A FIRING PIN SLIDABLY MOUNTED IN THE RECEIVER, A HAMMER MOUNTED FOR PIVOTAL IMPACT WITH SAID FIRING PIN, A PIVOTAL SEAR FOR RETAINING SAID HAMMER IN THE COCKED POSITION THEREOF, A FIRING LEVER PIVOTALLY MOUNTED IN THE RECEIVER FOR DISENGAGING SAID SEAR FROM SAID HAMMER FOR RELEASE THEREOF AGAINST SAID FIRING PIN, A LINK SECURED TO SAID FIRING LEVER TO DEPEND THEREFROM REARWARDLY OF THE PIVOTAL ENGAGEMENT OF THE LATTER IN THE RECEIVER, AND MEANS PIVOTED TO THE DEPENDING END OF SAID LINK FOR BLOCKING THE FIRING MOVEMENT OF SAID FIRING PIN DURING THE INTERVAL IN WHICH THE BARREL IS UNLOCKED, SAID FIRING PIN BLOCKING MEANS BEING RENDERED INOPERATIVE IN RESPONSE TO THE FIRING MOVEMENT OF SAID FIRING LEVER. 